Current test systems for units under test (UUT) such as multi-mode seekers that operate at multiple wavelengths include a number of spatially distributed discrete signal sources that provide multiple wavelength signals and are subject to mis-alignment in position and angle. Typically these sources can not be easily co-located or angularly co-aligned. Alternatively, discrete tests can be performed at different test stations configured to operate at different wavelengths. However, such test facilities require either or both of significant metrology that allows the transfer of the optical axis of the measurement chamber of one sensor to each of the chambers of the other sensors, or significant floor space so as to move the sources far a-field from the multimode seeker UUT. Another known structure is disclosed in U.S. Pat. No. 5,012,250, which discloses an infrared (IR) radiator disposed in a center of an RF horn radiator to provide an IR and a radiofrequency (RF) source. However, such structure suffers from compromised performance due to numerous infirmities including blockage imposed by the IR source in the RF radiator.